MajorAntituberculous antibiotic×Vitamin K antagonist anticoagulants
Updated · Methodology
Mechanism
Rifampicin induces CYP2C9, CYP3A4 and CYP1A2 – all main warfarin metabolism pathways. Warfarin requirement rises 2–3 fold. After rifampicin withdrawal sensitivity returns over 2–4 weeks, with bleeding risk if the dose is not titrated back down.
Symptoms
During use: subtherapeutic INR, thrombosis risk. After rifampicin withdrawal: sudden INR rise, bleeding risk.
Management
Monitor INR twice weekly for the first 4 weeks of rifampicin; increase warfarin by 25–100% as needed. After rifampicin withdrawal, frequent INR monitoring and downward titration.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Rifampin capsule (Ani Pharmaceuticals, Inc.) – Prescribing Information (2022)– ; DailyMed setid b389b1a3-672f-47e3-916c-4a9c044b211b
- DailyMed: Warfarin: FDA prescribing information, Drug Interactions section (DailyMed) (2024)
- AEMPS: Ficha técnica: Warfarina (Aldocumar 5 mg) (nº registro 63064), sección 4.5 (2023)– AEMPS, CIMA, nº registro 63064, revisión 01/2023, sección 4.5